CasaG90 Build in Houston

[fox]

David, perhaps you have a different density of ceramic fibre where you live but the stuff I use is quite dense and not easily compressible, certainly adding wire over four inches of ceramic fibre wont have any effect in any way other than holding it to shape and keeping it in place!

[david s]

From memory, I use 96 kg/m3 and there is a 128kg/m3, but being denser is a slightly poorer performer. Tightening the blanket reduces the amount of air in the volume thereby increasing density and reducing insulating capacity. As I said there are many ways to skin a cat with different preferred methods.

[broadrun96]

I would NOT drill and use tapcons on the actual dome, it will act as stress concentrator or possible point for cracks to start. If you notice on the FB video they drill into a concrete base not the oven.

That's exactly my problem with their descriptions, they show it screwed in to the dome on one thing and then screwed in to a base on another. I don't have a base under the dome except for the platform the oven will be built on. That would require screwing straight down and leave a screwhead where I would be either flaring out the stucco or a tile would be. They aren't exactly the most thorough with directions

[broadrun96]

The manufacturers build instructions should be followed, but I abandoned the use of lathe or chickenwire years ago for three reasons. Firstly getting the stuff to conform to a compound curve is difficult and time consuming, especially over a small oven. Secondly, having a highly conductive material in the insulating layer is counterproductive. I use a 10:1 3/4” (35mm) thick vermicrete layer over the blanket and this is sufficient to hold the blanket in place as well as evening out the uneven surface and restoring the spherical form. Lastly any compression of the blanket, caused by tightening the lathe or chickenwire will reduce its insulating capacity. I prefer to use random mixed reinforcing fibres in the outer rendered shell for much the same reasons.
However, there are many ways to skin a cat and every method has its advantages and disadvantages.

Would the vermiculite layer not also compress the insulation and the wire mesh, not chicken wire but the correct expanded mesh not distribute that load better? The purpose of the mesh is not to compress and be tight but rather be shaped at the insulation, yes that takes time but that's what I've seen for many projects of this and other designs

[fox]

I dont think a 10-1 vermiculite mix would compress ceramic fibre matting as the mix is a very lightweight in its self.

As David points out it can be done is several ways that all work just fine.

Personally I cant be bothered with vermiculite and I use 2 x 2” ceramic fibre blanket covered in several thin layers of fibre reinforced cement.

[broadrun96]

Which is why i asked in the thread for what the actual creator did with his. Not "expert" opinion about what they do outside of the manufacturer recs

[david s]

About to start on my Casa90, oven on site but the hearth still curing. The lift of the pieces is making me pause, damn they're heavy.

How did you secure the lathe over the insulation? Looks like tapcon screws, are they just directly in to the material of the dome? I have a 6'6 hearth pour and working on setting the base foam and floor this weekend but want to make sure I'm setting it right for the lathe. Just going to do the insulate and stucco cover rather than a custom mix, unless there are thoughts from the experts?

My apologies broadrun, but you did request thoughts from us. Only trying to help.